It is known practice nowadays to equip a firearm with a detachable release mechanism which can be detached from the firearm for cleaning, adjusting, repairing or changing. The known mechanisms however include drawbacks which jeopardize safety. If the release mechanism can be detached from the firearm, while the firearm is in a cocked state, the firearm might go off, which presents a formidable danger. Moreover the usual safety means are complicated and subject to disturbances.